This invention generally relates to devices and methods for performing a vascular anastomosis, and more particularly to stents for securing a graft vessel to a target vessel.
Vascular anastomoses, in which two vessels within a patient are surgically joined together to form a continuous channel, are required for a variety of conditions including coronary artery disease, diseases of the great and peripheral vessels, organ transplantation, and trauma. For example, in coronary artery disease (CAD), an occlusion or stenosis in a coronary artery interferes with blood flow to the heart muscle. In order to restore adequate blood flow to the heart, a graft vessel in the form of a prosthesis or harvested artery or vein is used to reroute blood flow around the occlusion. The treatment, known as coronary artery bypass grafting (CABG), can be highly traumatic to the patient""s system.
In conventional CABG a large incision is made in the chest and the sternum is sawed in half to allow access to the heart. In addition, cardiopulmonary bypass, in which the patient""s blood is circulated outside of the body through a heart-lung machine, is used so that the heart can be stopped and the anastomosis performed. In order to minimize the trauma to the patient""s system induced by conventional CABG, less invasive techniques have been developed in which the surgery is performed through. small incisions in the patient""s chest with the aid of visualizing scopes. Less invasive CABG can be performed on a beating or a non-beating heart and thus may avoid the need for cardiopulmonary bypass.
In both conventional and less invasive CABG, the-surgeon has to suture the graft vessel in place between the coronary artery and a blood supplying vein or artery. The suturing procedure is a time consuming, difficult process requiring a high level of surgical skill. In order to perform the suturing procedure, the surgeon must have relatively unobstructed access to the anastomotic site within the patient. As a result, in less invasive approaches which provide only limited access to the patient""s vessels, some of the major coronary vessels cannot be reached adequately, which can result in incomplete revascularization and a resulting negative effect on patient survival. Moreover, certain target vessels, such as heavily calcified coronary vessels, vessels having a very small diameter of less than about 1 mm, and previously bypassed vessels, may make the suturing process difficult or impossible, so that a sutured anastomosis is not possible.
Additionally, a common problem with CABG has been the formation of thrombi and atherosclerotic lesions at and around the grafted artery, which can result in the reoccurrence of ischemia. Moreover, second operations necessitated by the reoccurrence of arterial occlusions are technically more difficult and risky due to the presence of the initial bypass. For example, surgeons have found it difficult to saw the sternum in half during the next operation without damaging the graft vessels from the first bypass which are positioned behind the sternum.
Therefore, it would be a significant advance to provide a sutureless vascular anastomosis in which the graft vessels can be positioned on a variety of locations on target vessels having a variety of different diameters, which is easily performed, and which minimizes thrombosis associated with the anastomosis. The present invention satisfies these and other needs.
The invention is directed to anastomotic stents for connecting a graft vessel to a target vessel, and methods of use thereof. The anastomotic stents of the invention are suitable for use in a variety of anastomosis procedures, including coronary artery bypass grafting. The term xe2x80x9ctarget vesselxe2x80x9d refers to vessels within the patient which are connected to either or both of the upstream and the downstream end of the graft vessel. One embodiment of the invention comprises a large vessel anastomotic stent for use with large diameter target vessels such as the aorta or its major side branches. Another embodiment of the invention comprises a small vessel anastomotic stent for use on a target vessel which has a small diameter such as a coronary artery. Another aspect of the invention involves applicators for use with the stents of the invention. The terms xe2x80x9cdistalxe2x80x9d and xe2x80x9cproximalxe2x80x9d as used herein refer to positions on the stents or applicators relative to the physician. Thus, the distal end of the stent is further from the physician than is the stent proximal end. The proximal end of an implanted. stent is further from the center of the target vessel lumen than is the stent distal end.
The large vessel anastomotic stents of the invention generally comprise a substantially cylindrical body having a longitudinal axis, an open proximal end, an open distal end, a lumen therein, and at least one deformable section which radially expands to form a flange. The stent, with one end of a graft vessel attached thereto, is inserted into an incision in a wall of the target vessel with the deformable section in a first configuration, and the deformable section is radially expanded to a second configuration to deploy the flange. The flange applies an axial force, substantially aligned with the stent longitudinal axis, against the wall of the target vessel. Additionally, the flange is configured to apply a radial force, substantially transverse to the stent longitudinal axis, against the wall of the target vessel, to secure the stent to the target vessel.
In one embodiment of the large vessel stent, the stent has a single deformable section forming a flange, preferably on a distal section of the stent. However, a plurality of deformable sections may be provided on the stent. For example, in an alternative embodiment, the stent has a second deformable section on a proximal section of the stent. With the proximal and distal end flanges deployed, the stent is prevented from shifting proximally out of the target vessel or distally further into the interior of the target vessel.
The large vessel stents of the invention are configured to connect to target vessels of various sizes having a wall thickness of at least about 0.5 mm, and typically about 0.5 mm to about 5 mm. In one embodiment of the invention, the large vessel anastomotic stent is configured to longitudinally collapse as the deformable section is radially expanded. The surgeon can control the longitudinal collapse to thereby position the distal end flange at a desired location at least partially within the incision in the target vessel wall. Moreover, in the embodiment having a proximal end flange, the surgeon can control the position of the proximal end flange by longitudinally collapsing the stent to a greater or lesser degree, to thereby position the proximal end flange at a desired location in contact with the target vessel. Thus, regardless of the thickness of the target. vessel wall, the stent can be longitudinally collapsed to position the flanges against the target vessel wall and effectively connect the stent thereto. This feature is significant because the stent must be connected to target vessels which have a wide range of wall thickness. For example, the aortic wall thickness is typically.about 1.4 mm to about 4.0 mm. Therefore, regardless of the thickness of the target vessel wall, the degree of deployment of the proximal end flange, and thus the longitudinal collapse of the stent, can be controlled by the physician to thereby effectively connect the stent to the target vessel. For example, the surgeon may choose between partially deploying the proximal end flange so that it is positioned against an outer surface of the target vessel wall, or fully deploying the flange to position it in contact with the media of the target vessel wall within the incision in the target vessel wall.
In a presently preferred embodiment, the graft vessel is attached to the stent before insertion into the patient by placing the graft vessel within the lumen of the stent, and everting the end of the graft vessel out the stent distal end and about at least the distal deformable section. In a presently preferred embodiment, the graft vessel is everted about at least the section which contacts the media of the target vessel wall proximal to the distal deformable section, to facilitate sealing at the anastomosis site.
In a presently preferred embodiment of the invention, the deformable section on the large vessel stent comprises a plurality of helical members interconnected and disposed circumferentially around the stent. By rotating the distal end and the proximal end of the stent relative to one another, the helical members radially expand and the stent longitudinally collapses to form the flange. In a presently preferred embodiment, the distal flange is configured to deploy before the proximal end flange.
Another aspect of the invention comprises the applicators designed for introducing and securing the large vessel anastomotic stents of the invention to the target vessel. One such applicator is configured to apply torque and axial compressive load to the large vessel stent, to thereby radially expand the deformable section which forms the flange. The applicator of the invention may be provided with a sharp distal end, to form an incision in the target vessel wall through which the stent is inserted or to otherwise facilitate insertion of the stent into the target vessel wall. Another embodiment of the applicator of the invention includes a catheter member having one or more inflatable members designed to expand the incision in the target vessel and introduce the large vessel stent therein.
Another embodiment of the invention comprises small vessel anastomotic stents for use on small target vessels such as coronary arteries. The small vessel stents generally comprise an outer flange configured to be positioned adjacent an outer surface of the target vessel, and an inner flange configured to be positioned against an inner surface of the target vessel and connected to the outer flange. The outer and inner flanges generally comprise a body defining an opening, with one end of the graft vessel secured to the outer flange.
The small vessel anastomotic stents of the invention are used on small target vessels having a wall thickness of less than about 1.0 mm, and typically about 0.1 mm to about 1 mm. For example, small target vessels include coronary arteries. Despite the small size of the target vessels, the small vessel stents of the invention provide sutureless connection without significantly occluding the small inner lumen of the target vessel or impeding the blood flow therethrough.
In a presently preferred embodiment of the invention, the graft vessel is received into the opening in the outer flange and everted around the body of the outer flange to connect to the outer flange. In another embodiment, as for example when the graft vessel is a mammary artery, the graft vessel is connected to the outer flange by connecting members such-at sutures, clips, hooks, and the like.
The outer flange, with the graft vessel connected thereto, is loosely connected to the inner flange before insertion into the patient. The space between the loosely connected inner and outer flanges is at least as great as the wall thickness of the target vessel so that the inner flange can be inserted through an incision in the target vessel and into the target vessel lumen, with the outer flange outside the target vessel. With the outer and inner flanges in place on either side of a wall of the target vessel, tightening the flanges together compresses a surface of the graft vessel against the outer surface of the target vessel. This configuration forms a continuous channel between the graft vessel and the target vessel, without the need to suture the graft vessel to the target vessel wall and preferably without the use of hooks or barbs which puncture the target vessel.
In one embodiment of the invention, the inner flange is introduced into the target vessel in a folded configuration and thereafter unfolded into an expanded configuration inside the target vessel. The folded configuration reduces the size of the inner flange so that the size of the incision in the target vessel wall can be minimized. Folding the flange minimizes trauma to the target vessel and restenosis, and facilitates sealing between the graft and target vessel at the anastomotic site.
In a presently preferred embodiment of the invention, the inner and outer flanges are connected together by prongs on one member configured to extend through the body of the other member. However, the inner and outer flanges may be connected together by a variety of different types of connecting members such as sutures, hooks, clips, and the like. In a presently preferred embodiment, the flange members are connected together by prongs on the inner member configured to extend through the incision in the target vessel wall, without puncturing the wall of the target vessel, and through prong receiving openings in the body of the outer flange. The prong receiving openings in the outer flange may be configured to allow for the forward movement of the prong through the,opening to bring the inner and outer flanges together, but prevent the backward movement of the prong out of the opening, so that the inner and outer flanges remain substantially compressed together to seal the anastomotic site.
Another aspect of the invention comprises a small vessel stent applicator which facilitates introduction of the inner flange into the target vessel lumen, and connection of the inner flange to the outer flange around the target vessel. In one embodiment of the small vessel stent applicator, the applicator folds the inner flange into the folded configuration for introduction into the lumen of the target vessel.
Anastomotic systems of the invention may comprise combinations of the large and small vessel stents of the invention, for connecting one or both ends of a graft vessel to target vessels. Typically, in a coronary bypass using the anastomotic system of the invention, a large vessel stent connects the proximal end of the graft vessel to the aorta, and a small vessel stent connects the distal end of the graft vessel to an occluded coronary artery. However, it will be apparent to one of ordinary skill in the art that various combinations and uses of the anastomotic stents of the invention may be used. For example, in patients with an extreme arteriosclerotic lesion in the aorta, which may result in serious complications during surgical procedures on the aorta, the anastomotic stents of the invention allow the surgeon to avoid this region and connect the proximal end of the graft vessel to any other adjacent less diseased vessel, such as the arteries leading to the arms or head.
The large and small vessel stents of the invention are provided in a range of sizes for use on various sized graft vessels. Thus, the anastomotic stents of the invention can be used with venous grafts, such as a harvested saphenous vein graft, arterial grafts, such as a dissected mammary artery, or a synthetic prosthesis, as required.
Connection of the large vessel stent does not require the stoppage of blood flow in the target vessel. Moreover, the anastomotic stents of the invention can be connected to the target vessel without the use of cardiopulmonary bypass. Additionally, the surgeon does not need significant room inside the patient to connect the anastomotic stents of the invention to the target vessel. For, example, unlike sutured anastomoses which require significant access to the aorta for the surgeon to suture the graft vessel thereto, the anastomotic stents of the invention allow the proximal end of the graft vessel to be connected to any part of the aorta. All parts of the aorta are accessible to the large vessel stents of the invention, even when minimally invasive procedures are used. Consequently, the graft vessel may be connected to the descending aorta, so that the graft vessel would not be threatened by damage during a conventional sternotomy if a second operation is required at a later time.
The anastomotic stents of the invention provide a sutureless connection between a graft and a target vessel, while minimizing thrombosis or restenosis associated with the anastomosis. The anastomotic stents can be attached to the target vessel inside a patient remotely from outside the patient using specially designed applicators, so that the stents are particularly suitable for use in minimally invasive surgical procedures where access to the anastomosis site is limited. The stents of the invention allow the anastomosis to be performed very rapidly, with high reproducibility and reliability, and with or without the use of cardiopulmonary bypass.